linux-kernel - Re: [PATCH v7 1/4] iommu/io-pgtable-arm: Make pgtable walker more generic

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Message-ID: <20240823160929.GA851@willie-the-truck>
Date: Fri, 23 Aug 2024 17:09:29 +0100
From: Will Deacon <will@...nel.org>
To: Rob Clark <robdclark@...il.com>
Cc: iommu@...ts.linux.dev, linux-arm-msm@...r.kernel.org,
	freedreno@...ts.freedesktop.org,
	Mostafa Saleh <smostafa@...gle.com>,
	Rob Clark <robdclark@...omium.org>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	"moderated list:ARM SMMU DRIVERS" <linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 1/4] iommu/io-pgtable-arm: Make pgtable walker more
 generic

On Tue, Aug 20, 2024 at 10:16:44AM -0700, Rob Clark wrote:
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index f5d9fd1f45bf..b4bc358740e0 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -747,33 +747,31 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops,
>  }
>  
>  struct io_pgtable_walk_data {
> -	struct iommu_dirty_bitmap	*dirty;
> +	void				*data;
> +	int (*visit)(struct io_pgtable_walk_data *walk_data, int lvl,
> +		     arm_lpae_iopte pte, size_t size);
>  	unsigned long			flags;
>  	u64				addr;
>  	const u64			end;
>  };
>  
> -static int __arm_lpae_iopte_walk_dirty(struct arm_lpae_io_pgtable *data,
> -				       struct io_pgtable_walk_data *walk_data,
> -				       arm_lpae_iopte *ptep,
> -				       int lvl);
> +static int __arm_lpae_iopte_walk(struct arm_lpae_io_pgtable *data,
> +				 struct io_pgtable_walk_data *walk_data,
> +				 arm_lpae_iopte *ptep,
> +				 int lvl);
>  
> -static int io_pgtable_visit_dirty(struct arm_lpae_io_pgtable *data,
> -				  struct io_pgtable_walk_data *walk_data,
> -				  arm_lpae_iopte *ptep, int lvl)
> +static int io_pgtable_visit(struct arm_lpae_io_pgtable *data,
> +			    struct io_pgtable_walk_data *walk_data,
> +			    arm_lpae_iopte *ptep, int lvl)
>  {
>  	struct io_pgtable *iop = &data->iop;
>  	arm_lpae_iopte pte = READ_ONCE(*ptep);
>  
>  	if (iopte_leaf(pte, lvl, iop->fmt)) {
>  		size_t size = ARM_LPAE_BLOCK_SIZE(lvl, data);
> -
> -		if (iopte_writeable_dirty(pte)) {
> -			iommu_dirty_bitmap_record(walk_data->dirty,
> -						  walk_data->addr, size);
> -			if (!(walk_data->flags & IOMMU_DIRTY_NO_CLEAR))
> -				iopte_set_writeable_clean(ptep);
> -		}
> +		int ret = walk_data->visit(walk_data, lvl, pte, size);
> +		if (ret)
> +			return ret;
>  		walk_data->addr += size;
>  		return 0;
>  	}
> @@ -782,13 +780,13 @@ static int io_pgtable_visit_dirty(struct arm_lpae_io_pgtable *data,
>  		return -EINVAL;
>  
>  	ptep = iopte_deref(pte, data);
> -	return __arm_lpae_iopte_walk_dirty(data, walk_data, ptep, lvl + 1);
> +	return __arm_lpae_iopte_walk(data, walk_data, ptep, lvl + 1);
>  }
>  
> -static int __arm_lpae_iopte_walk_dirty(struct arm_lpae_io_pgtable *data,
> -				       struct io_pgtable_walk_data *walk_data,
> -				       arm_lpae_iopte *ptep,
> -				       int lvl)
> +static int __arm_lpae_iopte_walk(struct arm_lpae_io_pgtable *data,
> +				 struct io_pgtable_walk_data *walk_data,
> +				 arm_lpae_iopte *ptep,
> +				 int lvl)
>  {
>  	u32 idx;
>  	int max_entries, ret;
> @@ -803,7 +801,7 @@ static int __arm_lpae_iopte_walk_dirty(struct arm_lpae_io_pgtable *data,
>  
>  	for (idx = ARM_LPAE_LVL_IDX(walk_data->addr, lvl, data);
>  	     (idx < max_entries) && (walk_data->addr < walk_data->end); ++idx) {
> -		ret = io_pgtable_visit_dirty(data, walk_data, ptep + idx, lvl);
> +		ret = io_pgtable_visit(data, walk_data, ptep + idx, lvl);
>  		if (ret)
>  			return ret;
>  	}
> @@ -811,6 +809,20 @@ static int __arm_lpae_iopte_walk_dirty(struct arm_lpae_io_pgtable *data,
>  	return 0;
>  }
>  
> +static int visit_dirty(struct io_pgtable_walk_data *walk_data, int lvl,
> +		       arm_lpae_iopte pte, size_t size)
> +{
> +	struct iommu_dirty_bitmap *dirty = walk_data->data;
> +
> +	if (iopte_writeable_dirty(pte)) {
> +		iommu_dirty_bitmap_record(dirty, walk_data->addr, size);
> +		if (!(walk_data->flags & IOMMU_DIRTY_NO_CLEAR))
> +			iopte_set_writeable_clean(&pte);

Are you sure that's correct? I suspect we really want to update the actual
page-table in this case, so we probably want to pass the pointer in instead
of the pte value.

Will